Group communication refers to the data transmission to all terminals in a group simultaneously via a network in a rapid and effective manner. For a Long-Term Evolution (LTE) system, an end-to-end transmission delay for the group communication is required to be 150 ms. In order to meet the requirement on the transmission delay, it is currently inclined to reuse an existing Multimedia Broadcast Multicast Service (MBMS) architecture, with some modifications, as a network architecture.
FIG. 1 shows the MBMS network architecture for the LTE system. Logical entities in the MBMS network architecture mainly include a Mobility Management Entity (MME), an MBMS Gateway (GW), a Multi-cell/multicast Coordination Entity (MCE), an evolved Node B (eNB), a Packet Data Network Gateway (P-GW), and a Broadcast Multicast Service Center (BM-SC). An M3 interface is used to provide functions related to session management between the MME and the MCE, an M2 interface is used to provide functions, such as session management and MBMS scheduling information transmission, between the MCE and the eNB, and an M1 interface is used to provide MBMS service transmission between the MBMS GW and the eNB.
Depending on different roles for the group communication, the terminals for the group communication may be divided into two kinds, i.e., transmission terminals and reception terminals. The transmission terminal refers to a terminal which is authorized by a group communication server to transmit group communication data to the group communication server, and uplink data is transmitted in a unicast manner between the transmission terminal and the group communication server. On the other hand, the reception terminal refers to a terminal which is authorized by the group communication server to receive the group communication data issued thereby, and the group communication data may be received by the reception terminal via a network in a unicast or multicast manner.
Currently, there is an urgent need to support public safety group communication using the LTE system. One scheme is to achieve the group communication function using the existing MBMS network architecture. However, there is no scheme for notifying information related to the group communication, so as to meet the requirements of the group communication on service continuity when the terminals move into different Multicast Broadcast Single Frequency Network (MBSFN) areas or move out of the MBSFN areas.